Created
May 30, 2020 13:15
-
-
Save blrobin2/5a156e00c093b9d6be144fb4cb1c6d58 to your computer and use it in GitHub Desktop.
A way of representing the concept of a MAX_DATE or END_OF_TIME constant
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| const END_OF_TIME = new Date(parseInt('9'.repeat(15), 10)) | |
| // Thu Sep 26 33658 21:46:39 GMT-0400 (Eastern Daylight Time) | |
| // Example usage: default for date comparisons where you want to ensure the default is greater than | |
| // any of the provided dates | |
| const dateFromMMDDYYYY = mmddyyyy => new Date(Date.parse(mmddyyyy)) | |
| const dates = ['02/29/1984', '03/01/2055', '02/29/2244'] | |
| const earliest_date = dates.map(dateFromMMDDYYYY) | |
| .reduce( | |
| (earliest, date) => date < earliest ? date : earliest, | |
| END_OF_TIME | |
| ); | |
| // Of course in JavaScript, you could just do this: | |
| dates.reduce((earliest, date) => date < earliest ? date : earliest) | |
| // But if dates is an empty array, you'll get: | |
| // Uncaught TypeError: Reduce of empty array with no initial value at Array.reduce | |
| // You can think of this as a variation of the Null Object Pattern: https://en.wikipedia.org/wiki/Null_object_pattern | |
| // That is, no matter what data you'll be dealing with, you'll always end up with a Date, preventing scattering your | |
| // code base with null checks: | |
| if (earliest_date != null) { | |
| earliest_date.getFullYear() // or some other date check | |
| } | |
| // or, more accurately in a Duck Typing world: | |
| if (earliest_date != null && typeof earliest_date.getFullYear === 'function') { | |
| earliest_date.getFullYear() | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment